Fallout From High-Frequency Trading Hits Brokerages

Brokerages that cater to mom-and-pop investors are emerging as an early victim of the intensifying scrutiny of high-speed trading.

Shares of E*Trade Financial Corp., Charles Schwab Corp. and TD Ameritrade Holding Corp. tumbled last week amid concerns that regulators would ban a practice that allows brokerages to collect hundreds of millions of dollars a year in revenue by selling orders to middlemen who use high-frequency strategies...